#include <mlibc/thread-entry.hpp>
#include <mlibc/all-sysdeps.hpp>
#include <mlibc/tcb.hpp>
#include <bits/ensure.h>
#include <sys/mman.h>
#include <errno.h>
#include <stdint.h>
#include <stddef.h>

extern "C" void __mlibc_enter_thread(void *entry, void *user_arg, Tcb *tcb) {
	// Wait until our parent sets up the TID.
	while(!__atomic_load_n(&tcb->tid, __ATOMIC_RELAXED))
		mlibc::sys_futex_wait(&tcb->tid, 0, nullptr);

	if(mlibc::sys_tcb_set(tcb))
		__ensure(!"sys_tcb_set() failed");

	tcb->invokeThreadFunc(entry, user_arg);

	auto self = reinterpret_cast<Tcb *>(tcb);

	__atomic_store_n(&self->didExit, 1, __ATOMIC_RELEASE);
	mlibc::sys_futex_wake(&self->didExit);

	mlibc::sys_thread_exit();
}

namespace mlibc {

static constexpr size_t default_stacksize = 0x200000;

int sys_prepare_stack(void **stack, void *entry, void *user_arg, void *tcb, size_t *stack_size, size_t *guard_size, void **stack_base) {
	if (!*stack_size)
		*stack_size = default_stacksize;
	*guard_size = 0;

	if (*stack) {
		*stack_base = *stack;
	} else {
		*stack_base = mmap(nullptr, *stack_size, PROT_READ | PROT_WRITE,
						MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
		if(*stack_base == MAP_FAILED) {
			return errno;
		}
	}
	
	uintptr_t *sp = reinterpret_cast<uintptr_t *>(reinterpret_cast<uintptr_t>(*stack_base) + *stack_size);

	*--sp = reinterpret_cast<uintptr_t>(tcb);
	*--sp = reinterpret_cast<uintptr_t>(user_arg);
	*--sp = reinterpret_cast<uintptr_t>(entry);
	*stack = reinterpret_cast<void*>(sp);
	return 0;
}

} //namespace mlibc